Ignorant fool plugs 30 amp rv into 220

[jmsokol]

The TT-30 looks exactly like the outlet in my parent's house for the dryer,, I mean EXACTLY in fact the plug fits.

Hey guys,

I'm Mike Sokol from NoShockZone. Thanks for linking to my article about mis-wired TT-30 outlets. I would say that 30-amp Dryer and RV outlets look VERY similar, but they definitely are NOT the same receptacle. And I would guess that it's nearly impossible to force a 30-amp/120-volt RV shore power plug into a 30-amp/240-volt Dryer outlet. You can see how different they are in my graphic below.

That being said, while the TT-30 RV receptacle is clearly marked for 125 volts maximum, it really looks like it should be a 240-volt service. And I would guess that your average home electrician has seen zero RV outlets, but wired dozens or even hundreds of 240-volt dryer outlets in his day. But, he really is paid to know what he's doing, and should be insured. So if he goofs up and destroys your RV's electrical system, he should pay for his mistake.

And yes, I too have been on dozens of forum threads with this exact failure scenario, sometimes costing 10's of thousands of dollars to repair. So its up to each of us to understand enough how to test EVERY new power outlet for proper grounding and voltage BEFORE we plug an RV into it. And do this even if you've just paid an electrician to wire in a pedestal outlet for your RV at your home. This is especially important for RV 30-amp shore power outlets because of the 120/240-volt confusion.

Mike Sokol

 

[John From Detroit]

Mike you show ONE dryer outlet,, I have seen several different designs, including the one at my parent's house, which was different from the one you show.    And in addition there are air compressors, welders and more. Plugging a 30 amp trailer into at least one of those is very very very very easy and happens more often that I care to read about.

True story: Was at a Moose Lodge and the governor ask if Id plugged into their 60 amp outlet.. (I did not find it but I had seen the circuit breaker box so knew that it was 240 volt already)

But then.. I know my way around a volt meter.

 

[jmsokol]

Mike you show ONE dryer outlet,, I have seen several different designs, including the one at my parent's house, which was different from the one you show.    And in addition there are air compressors, welders and more. Plugging a 30 amp trailer into at least one of those is very very very very easy and happens more often that I care to read about.

Here's a chart of all NEMA receptacles used in the USA. The 10-30R was (and still is) the most common 3-wire dryer outlet originally used in the 60's to save the cost of the 4th (ground) a wire. And you can still buy this type of plug and outlet at any big box store. But now a 4-wire 30-amp/240-volt receptacle is required for new dryer installations. There may be other types of receptacles that were used in old installations, and I've even seen standard 120-volt Edison outlets intentionally mis-wired to 240-volts for an air compressor or floor polisher. Those are REALLY dangerous for any appliance plugged into them.

The key thing is to test any unknown outlet for proper grounding and voltage before plugging in your expensive RV, especially if it's a 30-amp/120-volt TT-30 connection. Here's a video I made of how to test a campground pedestal for proper power. https://www.youtube.com/watch?v=W5pLlZm8O84

 

[Frizlefrak]

When we bought his house, it had a 30 Amp RV outlet already installed outside by the previous owner.  This was long before I had been schooled on this particular issue by this forum.  I remember being reluctant to plug into it the first time fearing it was a 220.  I finally stuck the probes on my multi-meter in....lo and behold, 110 (whew).  That said, any electrician worth his salt should have ASKED the owner what he intended to use the outlet for and wired it accordingly. 

 

[John From Detroit]

I have to ask.. If there is no outlet used for dryers, air compressors, welders and such that is not identical to a TT-30

How come so many people plug into such an outlet in a friend's garage and ZZZZAAAAAPPPPPP Let all the magic smoke out?

 

[jmsokol]

I have to ask.. If there is no outlet used for dryers, air compressors, welders and such that is not identical to a TT-30

How come so many people plug into such an outlet in a friend's garage and ZZZZAAAAAPPPPPP Let all the magic smoke out?

All 240-volt outlets for dryers, welders, compressors (etc...) have their own form factor and will not accept a 120-volt TT-30 shore power plug. However, while the RV TT-30 outlet is unique and supposed to be wired only for 120 volts, sometimes it's mis-wired on purpose to 240-volts just because someone needed it for a non-standard plug they improperly installed. I think that's because a TT-30 outlet looks like it "should" be 240 volts. But it's definitely NOT code compliant to wire one for 240 volts.

The other (more common) thing that happens is an electrician or DIY guy confuses a TT-30 outlet with the 3-wire dryer outlet and accidentally wires it to 240 volts. And even if you instruct your electrician that it's supposed to be 120 volts, don't count on that happening. I taught a No~Shock~Zone clinic at a big RV repair shop last year, and the service manager said they paid a licensed electrician to install four TT-30 outlets in their service bays. The electrician argued with them that they needed to be wired for 240-volts, but it wasn't until they showed him my article on mis-wired TT-30 outlets that he relented and wired them for 120 volts. So if an electrician will argue with a huge RV service shop, what chance does a homeowner have? It's a good idea to always test any unknown TT-30 outlet for proper voltage, polarity and grounding BEFORE you plug in your RV's shore power.

Mike Sokol

 

[Lou Schneider]

You can buy replacement plugs that can be configured to fit either the 120 volt TT-30 or the 240 volt NEMA 10-30 socket - the plug comes with ground pins for each type and you fit the one you want into the plug body.

Someone who doesn't understand the difference buys a TT-30, wires it up for 240 volts, then puts the matching ground pin on the plug for the 240 volt dryer or  welder that will plug into that socket - everything's fine until someone else tries using that outlet to power an RV.

 

[John From Detroit]

Well as I said Mike, I see two types of threads where someone plugs into 240 volts.

1: Hired the TT-30 installed (one case the guy did it himself)

2: Plugged in to an existing outlet in a  garage (Without checking)

Occasionally I hear of a goof at a campgrond but those are rare, very rare, (like perhaps once in well over a decade).

But dozens of garage outlets and professionally installed TT-30s

If the plug won't fit, how are they plugging into it?

I'm fairly sure the 60 amp outlet I did NOT plug into at the Falls of the Rough (KY) Moose lodge wold take a TT-30 as well, however as I said, I did not plug into it, (I knew it was 240 volt even before I located it). but .. That's cause I know things.
(Like where the double ganged 60 amp circuit breakers were located so when the lodge governor ask about the 60 amp circuit, I knew all 60 amp circuits in that box were 240 volt already)  Oh, I did find the outlet

 

[Tom]

This discussion validates my prior discussion with a boat manufacturer when we had 50A power installed on our docks at the house; The manufacturer questioned why I needed a diagram for the main power into the boat, and they were insistent that "an electrician will know the correct way to hook up the dockside receptacle". My response:

"I won't be taking any chances, and I've warned the electrician that, if he plugs my boat in before I've checked out his installation, I'll chop his fingers off".

FWIW the boat has mixed 240V and 120V equipment. Heat/Air pumps and stovetop are 240V, most other appliances are 120V.

 

[PatrioticStabilist]

I almost did it on our last motorhome, it was 30 amp.  Tom had wired an outlet in his shed for his electric welder.  I looked at it and it was the same as ones at the RV park.  The only reason I didn't is I couldn't get it unplugged, I think he had fixed it so it couldn't be.  I told him and he said good thing you didn't.  So yep another almost fool.  But after that he labeled it!!

 

[jmsokol]

I almost did it on our last motorhome, it was 30 amp.  Tom had wired an outlet in his shed for his electric welder.  I looked at it and it was the same as ones at the RV park.  The only reason I didn't is I couldn't get it unplugged, I think he had fixed it so it couldn't be.  I told him and he said good thing you didn't.  So yep another almost fool.  But after that he labeled it!!

I'm guessing he bought a TT-30 outlet and plug, and mis-wired it for 240 volts, instead of the 120 volts it's rated for right on the plug. See the first attached picture for the TT-30 outlet. See the second attached picture for a Welder 30-amp/240-volt outlet. I would say there's no way to force a RV 30-amp/120-volt plug into a Welder 30-amp/240-volt outlet. 

So, because DIY guys and contractors will wire up whatever they have handy, I'm still taking the position that you should double-check all unknown 30-amp shore power outlets for the correct 120-volts BEFORE plugging in your RV.

 

[PatrioticStabilist]

I don't remember now and it was before we bought this motorhome which is a 50 amp.  I know before we sold the house he took it out.

 

[Rene T]

This was a test ;D

 

[eaglestar]

I know I'm a little late chiming in here. If you check a good NEMA chart you can see that a 7-20 is almost identical to a TT-30, but it's a 277-volt connector. Any electrician worth his tool belt should know that a device with a U-ground and two diagonal blades is NOT 220/240-volt, even if he doesn't recognize the configuration. The closest 220 has a blade ground, not a U. That said, except for the standard 120-volt 5-15 and 5-20 outlets, I ALWAYS meter probe an outlet I haven't used and didn't wire myself. I've seen too much weird stuff to trust anyone's wiring.

 

[inscop]

I bought myself a 30A surge guard with idiot lights.  I test EVERY time before I hook up, even in state parks.  Search for 30A RV surge guard or 30A RV surge protector, unless you need a 50A.